Power system



J. M. PESTARINI POWER SYSTEM Filed Sept. 21, 1938 5 Sheets-Sheet 1 Fig. 10.

Fig. 1|.

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m 1 Pt n O tmmflc M t 6 7A Vh ms mp i Ampere-turns.

J1me 1940. J. M. PESTARINI 2,203,544

POWER SYSTEM Filed Sept. 2l, 19 58 3 Sheets-Sheet 2 Fig. l.

Fig. 2.

Partial/y open Ihventor': Joseph M. Pestar'ini,

. Han/176: AM by His Attorney.

June 4, 1940. J. M. PESTARINI POWER SYSTEM Filed Sept. 21, 1938 3 Sheets-Sheet 5 Fig.4.

Voltage o WELB wLmQEW LO mtmLLnu Voltage Fig. 9.

Invefitor: Joseph M. Pescar'ini, by x 6,49

His Attorney.

Patented June 4, 1940 UNITED STATES PATENT OFFICE 19 Claims.

My invention relates to power systems wherein a prime mover is arranged to drive a generator supplying current to an electrical load.

Electrical power systems are often used in transportation for driving self-propelled vehicles or ships wherein an engine drives a generator which is arranged to supply power to the driving motors. In such a system, the engine generally is a substantially constant torque and constant speed prime mover, and it is desirable that the main electric generator driven by the prime mover should develop substantially constant power over the major portion of the operating range when operating at the maximum efliciency speed of the prime mover, and it also is desirable that the generator should have such a characteristic that the load current and voltage does not exceed a predetermined maximum limiting value.

An object of my invention is to provide a generator having an excitation system arranged to provide a substantially constant power characteristic over the major portion of the normal operating range thereof, and a current and voltage limiting characteristic for maintaining the current and voltage within safe limiting values.

Another object of my invention is to provide a power system wherein a prime mover is arranged to drive a generator for supplying substantially constant power to an electrical load over the major portion of the normal operating range, and arranged to limit the current and voltage of the generator and thereby limit the power developed to safe operating values.

Further objects and advantages of my invention will become apparent and my invention will be better understood from the following description referring to the accompanying drawings, and the features of novelty which characterize my invention will be pointed out with particularity in the claims appended to and forming part of this specification.

In the drawings, Fig. 1 schematically illustrates a power system wherein a prime mover is arranged to drive a generator having a substantially constant power output characteristic over the major portion of its operating range and a currentlimiting and voltage-limiting characteristic for limiting the voltage and current of the system to safe operating values; Fig. 2 represents a modification of the system shown in Fig. 1; Fig. 3 represents the general characteristics of a system such as that shown in Figs. 1 and 2; Figs. 4 and 5 represent the operating characteristics of the system shown in Fig. 1; Fig. 6 represents the operating char- 55 acteristics of various elements of the power system shown in Fig. 11; Fig. '7 represents the operating characteristics of different elements of the power system shown in Fig. 9; Fig. 8 represents operating characteristics of the power system shown in Fig. 2; Fig. 9 is another and the pre- 6 ferred embodiment of my invention and represents a power system somewhat similar to Fig. 1; Fig. 10 represents a further modification of my invention somewhat similar to the system arrangement shown in Fig. 9; Fig. 11 is another 10 modification of my improved power system, and

is somewhat similar to the arrangement shown in Fig. 10; Fig. 12 represents the operating characteristics of an auxiliary exciter in the power system shown in Fig. 10; and Fig. 13 represents the operating characteriscs of various elements of the power system shown in Fig. 10.

Referring to the drawings, I have shown in Fig.

1 a substantially constant torque prime mover I, such as a Diesel engine, arranged to drive a main generator 2 of the metadyne or armature reaction excitation type through a shaft 3. Essentially, a dynamo-electric machine of the metadyne type is a direct-current dynamo-electric machine having a rotor or armature provided with windings and a commutator of the conventional direct-current dynamo-electric machine type, and a stationary member providing a path of low magnetic reluctance to the magnetic fluxes set up by the armature currents. The commutator of 3 a bipolar machine usually is provided with two brush sets electrically displaced from each other for providing a primary circuit and a secondary circuit through the metadyne rotatable member or armature. The brush set which is arranged to provide the primary armature circuit usually is arranged to maintain the electrical potential across the primary circuit substantially constant and may be short circuited or connected across a substantially constant potential source of electrical power supply and the other brush set carries a direct-current of substantially constant magnitude. The stationary member of the metadyne also may be provided with various field exciting windings arranged to provide the meta- 5 dyne with special characteristics and to insure the stability of the machine.

The main metadyne generator 2 is provided with an armature and a commutator similar to that of a conventional direct-current dynamoelectric machine. Two sets of brushes are arranged about the commutator, and one of these sets of brushes 4 and 5 is connected across an electric battery 6 which provides a substantially constant potential source of electrical power supply, and these brushes 4 and 5 provide a primary circuit through the armature 2 and, therefore, form the primary brush set. Another set of brushes 1 and 8 is electrically and anguiarly displaced about the commutator from the primary brushes 4 and ii, and is connected to an electrical load comprising motors ii and provides a secondary circuit through the generator armature 2 and, therefore, forms the secondary brush set.

The main metadyne generator is provided with a stator arranged to provide a path of low magnetic reluctance to the fluxes set up by the ar mature currents, and a field exciting winding it] is arranged to magnetically excite the main gen-= erator and control its operating characteristics.'

This field exciting winding it) generally is called a varlator field exciting winding, as it varies or controls the characteristics of the main generator.

The variations in the energization of the variator field exciting winding are obtained controlling the excitation of an auxiliary metadyne ex-= citer M arranged to energize this variator winding. The excitation of the auxiliary metadyne ii] is controlled automatically and inherently in such a manner as to maintain substantially constant power output by the main metadyne generator over the major portion of its operating range and to provide a drooping voltage-current characteristic to the main generator over a portion of its operating range for limiting the maximum volt age and current to safe operating values. The metadyne exciter ii is provided with arma ture and commutator which are similar to that of a conventional direct-current dynamo-el m tric machine armature and commutator, and is driven in a predetermined speed relation to speed of the prime mover t through the shaft Two sets 0; brushes are arranged about the aux= iliary metadyne commutator, and one oi these sets or brushes 6?. and i3 is connected across the electric battery 5 and provides a primary cir== cuit through the armature i i, and forms the primary brush set, and. another set of brushes G6 and it is electrically displaced from the primary brushes i2 and lit and is connected to the main generator field exciting winding These brushes Ml and 65 provide a secondary circuit through the armature i l and form the secondary brush set of the auxiliary metadyne exciter. stationary member also is arranged to provide a path of low magnetic reluctance to the fluxes set up by the auxiliary metadyne armature currents, and is provided with two field exciting windings i6 and l i arranged to control the operating char acteristics of the auxiliary metadyne dynamoelectric machine l l. The field exciting winding 06 is energized by an auxiliary dynamo-electric machine l8, which is driven in a predetermined speed relation to the speed of the other rotating machines and the prime mover by the shaft 8. The auxiliary dynamo-electric machine ill is provided with a field exciting winding i9 connected across the battery 6 in order to provide it with a substantially constant component of excitation. Another field exciting winding 20 is provided for the auxiliary exciter l8 and is connected across the secondary brushes l and 8 of the main generator 2 so as to provide a component of excitation which varies in accordance with an electrical characteristic of the main generator; namely, the secondary voltage thereof. The field exciting winding 20 is 1 field exciting windings provides the auxiliary exciter l8 with a voltage characteristic which is substantially constant for low main generator secondary voltages and which falls off very rapidly at high main generator secondary voltages, thus providing the auxiliary exciter 3 with the type of characteristic which is generally desirable for limiting the voltage and current of the machine. Fig. 3 shows the general characteristics of a system illustrative of the general case wherein the dynamo-electric machine is provided with excitation, giving it a drooping voltage-current characteristic a--bc-tZ-e which limits the current and voltage to saie operating values.

It is desirable that the main generator also should have a substantially constant power characteristic in order to obtain the maximum eificiency from the prime mover over the major portion of its operating range, and this constant power characteristic may be represented by a hyperbolic voltage-current characteristic, such as bfd in 3. Therefore, it is generally desirable that the dynamo-electric machine be provided with an excitation over part of its opcrating range which will provide a voltage-cur rent characteristic corresponding to the portions ab and d-e oi the curve a-bc-de and a main operating range voltage-current charac teristic represented by the curve bf-d.

inc operation of the excitation system in i. will be better understood by reference to Figs. and 5. In 4, the curves represent the relation between the field exciting winding ampare-turns and voltages. The curve ab repre-= sents the relation of the constant ampere-turns s provided by the field exciting windin ill with respect to the terminal voltage of the auxiliary exciter ill or the main generator secondary voltage. The curve o-c represents the relation be tween the ampere-turns provided by the field ex citing winding 2@ and the main generator se ondary terminal voltage. The curve ad represents the relation between the resultant ampereturns of the field exciting windings 09 and 8G and the main generator terminal voltage across the brushes l and 8. The curve orZ--cb is a magnetization curve for the auxiliary exciter i8 and represents the relation between the field excitation and terminal volts oi the auxiliary exciter I18. the terminal volts of the auxiliary exciter i8 and the secondary voltage across i... brushes 2 and 8 of the main metadyne generator l3, produced by the excitation represented by the curve and ooZ-c--b of Fig. 4. Since the load connected to the terminals of the auxiliary exciter 08 consists only of the field exciting winding 36, the curve a-bc-d--e in Fig. 5 also represents the relation of the current through this field exciting winding M5, and consequently, the ampere-turns of'this field exciting winding with respect to the secondary terminal voltage of the main metadyne generator '2. The field exciting winding i6 is arranged along the secondary commutating zone of the auxiliary metadyne exciter H and is energized so as to produce an excitation in opposition to the secondary armature reaction of the auxiliary metadyne armature. This type of field exciting winding functions asa variator field exciting winding, as it varies the relation 01' the secondary current with respect to the primary armature voltage; The operation of a variator field exciting winding arranged on a metadyne dynamo-electric machine has been explained in my U. S. Patent No. 1,987,417, Janu- Fig. 5 illustrates the relation between Ell my 8, 1935. As explained in my above patent, any variation in the excitation provided by the variator field exciting winding Ii produces an inverse transient variation in the resultant excitation along the secondary commutating zone of the metadyne, which in turn produces a variation in the counter-electromotive force induced by the excitation along the secondary commutating zone between the primary brushes l2 and I3 of the metadyne corresponding to the resultant secondary excitation. This transient variation in the counter-electromotive force results in a variation of the primary armature current in the opposite sense to the variation of the counterelectromotive force and in the same sense as the excitation of the variator field exciting winding Hi. This results in a variation in the secondary voltage between brushes l4 and IS, in the same sense as the variation in the excitation provided by the variator field exciting winding l6, and since this secondary voltage is impressed across the field exciting winding III of the main generator 2, the secondary current of the metadyne exciter I I, and consequently the current and excitation of the field exciting winding l vary in accordance with the excitation produced by the variator field exciting winding l6. Thus, it is clearly seen from the characteristic curve shown in Fig. 5, that the energization of the field exciting winding l0 will remain substantially constant for a given range of operating voltage of the main generator 2, and will fall off very rapidly beyond a predetermined secondary voltage of the main machine when controlled only by the auxiliary exciter I8. The field exciting winding I0 is arranged to produce excitation along the secondary commutating zone of the main metadyne generator 2, which is opposed to the secondary armature reaction of the main metadyne generator armature, and operates in the same manner as the field exciting winding l6 so that any variations in the excitation produced by the generator field exciting winding It! produces a corresponding variation in the secondary current of the main metadyne generator 2.

As has been stated, the prime mover l is a substantially constant torque machine, and consequently for any given speed, it will develop a substantially constant power output. In order to utilize the prime mover at its maximum efficiency, it is desirable that the generator characteristic of the main metadyne generator 2 should vary as a hyperbolic relation between the secondary terminal voltage of the brushes 1 and 8 and the secondary load current. It is also desirable that the maximum power developed by the main metadyne generator 2 remain within the safe electrical operating limits of the generator 2, as well as within the safe mechanical operating limits of the prime mover l. The limits of the power generated by the main generator may be controlled by the energization of the field exciting winding I0, so that beyond a predetermined secondary voltage of the main generator 2, the secondary load current will decrease very rapidly, and beyond a predetermined secondary load current of the main generator 2, the current will remain substantially constant, and the secondary terminal voltage will decrease very rapidly. In this manner, the voltage and current of the main metadyne generator may be very definitely limited by the excitation provided by the field exciting winding Ill. Since the prime mover is a substantially constant torque source of power when it is regulated to operate at substantially constant speed, it will provide a substantially constant power for any given fuel supply, and there will be a particular operating speed at which it will operate at maximum efficiency. It, therefore, is desirable that the generator should have a substantially constant power characteristic over the greater part of its operating range, and this preferably should occur at the maximum efliciency speed of the prime mover l.

In order to stabilize the operation of the system, I provide a field exciting winding l'la arranged to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter ll so as to vary the secondary current thereof, and therefore, to vary the energization of the field exciting winding III on the main generator 2. This stabilizing field exciting winding is connected across a secondary winding 93 of a transformer energized by a primary winding 94 connected to the secondary load circuit of the main generator. The excitation produced by this field exciting winding l'la may be in either direction, and the field exciting winding is arranged and connected to the transformer so that it will provide a component of excitation along the secondary axis of the metadyne exciter II which is opposed to any armature reaction or main component of magnetic excitation which would tend to produce alternating, transient, or oscillating currents in the secondary circuit thereof which might be reproduced or amplified in the secondary or load circuit of the main generator 2. In this manner, alternating, transient, or oscillating current will be effectively neutralized and suppressed and the stable operation of the system maintained.

Since the arrangement of the field exciting winding l6 will provide an energization of the field exciting winding H], in accordance with the curve shown in Fig. 5, it is necessary that the excitation of the auxiliary metadyne exciter ll be varied in order to obtain a hyperbolic characteristic relation between the secondary load current and the secondary voltage of the main metadyne generator 2. The field exciting winding I1 is connected across an auxiliary generator 2| and in series with the electric battery 6. The armature of the auxiliary generator 2i is driven by the shaft 3 in a predetermined speed relation to the speed of the other rotating machines and the prime mover, and is provided with a shunt field exciting winding 22 in order to obtain a more rapid and sensitive response to variation in the speed operating characteristic of the prime mover and rotating machines driven thereby. This machine is arranged to operate as an unsaturated generator so that small variations in speed will produce relatively large variations in its generated voltage, and it is so constructed and arranged that its terminal voltage will be equal to the voltage of the electric battery 6 when the speed of the prime mover l reaches the speed at which the prime mover operates at its maximum efficiency. In this manner, when the prime mover operates at its maximum efliciency speed, the voltage of the auxiliary generator 2! will be exactly equal to the voltage of the electric battery 6, and no current will flow through the field exciting winding IT, as this winding is energized in accordance with the difference in potential between the constant battery voltage and the variable voltage of the auxiliary generator 2| which depends upon the speed of the prime mover I.

The operation of this type of excitation system is described in my U. S. Patent No. 2,038,384, April 21, 1936, and provides the auxiliary metadyne exciter li with a constant power characteristic represented by the curve b-f-d in Figs. 3 and 5.

Referring to these figures, it is desirable that the main metadyne generator 2 should have a characteristic a-b in order to limit the current to a safe operating value, that it should have a hyperbolic operating characteristic h;f-d so that it will utilize the prime mover at its maximum eificiency over the major portion of its operating range, and that it should have 2. voltage limiting characteristic de in order to limit the voltage of the generator to a safe operating range. As has been explained, the generator may be provided with a characteristic ab and tZ-e by the variator field exciting winding it, as determined by the excitation of the field exciting winding 65. It is, therefore, desirable the field exciting winding ill of the auxiliary meta dyne exciter it should be inoperative during that portion oi the operating range of the main generator 2 which is determined by the current or voltage limiting generator characteristics u-b and d-c respectively, and that the excitation provided by the field exciting winding i should correspond to the hyperbolic characteristic b-f-d for all values intermediate the operat ing points 2) and d of the operating characteristics of the main generator 2. in order to obtain the hyperbolic characteristic b--f-d, the field exciting winding ill is arranged to produce an excitation which is opposed to the excitation provided by the field exciting winding 5 and of such magnitude that the secondary voltage between the brushes M and of the auxiliary exciter metadyne it will have a hyperbolic relaticn to the secondary voltage of the main metadyne generator across brushes 3 and 8. As ex plained with respect to Fig. 5, the curve representing the relation between the energization of the variator field exciting winding and the secondary voltage of the metadyne, corresponds to the curve representing the relation between the secondary current of the metadyne and the secondary terminal voltage thereof. Therefore, it may be said that it is desirable that the energize.- tion of the variator field exciting winding id should correspond to the curve a--b-frl-c shown in 5.

Since the variator field exciting winding 66.

will provide the main metadyne generator 2 with the characteristic a--b and de without the use of the field exciting winding til, a device is arranged to deenergize the field exciting winding it when the secondary current and voltage of the main metadyne generator 2 bear the relations represented by the points i) and d in Fig. 5. This device includes a switch provided with a contact 23, connected to one terminal of the field exciting winding I1, and another contact M connected to the other terminal of the field exciting winding l1 and to a brush 25 of the auxiliary generator 2! to which the field exciting winding I! is connected. An oscillatable sliding contactor 21 is arranged to complete an electrical circuit through the contact 23, and a field exciting winding 28 of a dynamo-electric relay 29 to the battery 6. The relay 29 includes a rotatable member which is connected across the battery 6 through a resistance 30 arranged to limit the current through the rotatable member. Since the voltage of the auxiliary generator 25 may be higher, lower, or equal to the voltage of the electric battery 6, the current which flows through the field exciting winding 28 may provide an excitation in one direction or another, or no excitation at all, depending upon the relative direction and magnitude of the current flowing between the auxiliary generator 2i and the electric battery The rotatable member 29 is connected by a shaft 3i to the arcuately oscillatable contactor 2'17, and the direction and magnitude of the torque exerted by the rotatable member is dependent upon the excitation provided by the field exciting winding It is obvious that when the speed of the prime mover is such that the voltage of the auxiliary generator it exactly equals the voltage of the electric battery no current will flow therebetween, and the field exciting winding will be deenergized, so that no torque will be exerted by the rotatable member 29. This is the condition which is obtained at the points b and d of the characteristic curve shown in Fig. 5, for at these points of the operating characteristic, the variator field exciting winding it provides the auxiliary metadyne exciter it with an excitation such that the excitation of the variator field exciting winding iii is such that the relation of the secondary voltage and current of the main metadyne generator is that represented by the points h and d. For any points on the operating characteristic intermediate the points I) and d, the field exciting winding 56 will tend to provide an excitation to the field exciting winding it which would give the main metadyne generator a voltage-current characteristic similar to that shown by the dotted curve b-CZ. However, for any operating point intermediate b and d, along the curve c-d, the generator 2 will tend to overload the prime mover and tend to reduce the speed oi the prime mover. Such reduction in speed will cause a reduction in the voltage generated by the auxiliary generator 2!! so that current will tend to flow from the battery 6 to the dynamo-electric machine 2i, and will tend to drive this machine as a motor. The field exciting winding of the relay 29 is arranged so that such a direction of current flow causes the relay 29 to exert a torque in a clockwise direction, and completes a circuit between the contactor 2V and contact 28, so that current flows through the field exciting winding il which produces an excitation in opposition to the excitation produced byv the field exciting winding 0 This reduces the secondary voltage of the auxiliary metadyne exciter Ill, and consequently, reduces the energization of the variator field exciting winding Hi. This, in turn, reduces the excitation produced by the field exciting winding iii, producing a corresponding reduction in the secondary voltage between the brushes and ti and the secondary current of the main metadyne generator. This reduction in secondary voltage and current of the main metadyne generator is represented by the diiference between the ordinates and abscissas, respectively, of the curve bc-d and the curve bf--d in Fig. 5. In this manner, the operating characteristic between the points I) and d is made to follow the hyperbolic curve bfd, as any variation from the constant power output curve b-f-d will tend to produce a variation in the excitation of the field exciting winding i7, so as to maintain the power developed by the main metadyne generator 2 substantially constant. acteristic of the main metadyne generator 2 When the operating charbecomes such that either the voltage or the current reaches the point d or b, respectively, the current through the field exciting windings l1 and 29 will be reduced to zero; Under this condition, the field exciting winding [1 has no effect on the main generator characteristic, and the relay 29 is substantially torqueless.

When the operating characteristic of the main metadyne generator 2 is such that it follows the relation represented by the curves a--b or de, the power generated by the main generator 2 is less than the power developed by the prime mover l, and the speed of the prime mover, and the rotating machines, will tend to increase. Therefore, it is desirable that along these portions of the operating characteristic of the main metadyne generator 2, that the fuel intake of the prime mover I should be less than that required for its operation at its maximum efilci'ency speed, so that the power developed by the prime mover will be limited to that required by the generator characteristic. In order to vary the fuel intake of the prime mover to obtain this decrease in power developed, a throttle controlling mechanism is provided which includes a gear wheel 32 mounted on the shaft 3| and arranged to move a gear rack 33 connected to a throttle control lever 34. Springs 35 and 36 are arranged to bias the throttle gear rack 33 to a position which provides the prime mover I with a fuel supply corresponding to the maximum efiiciency speed position. Whenever relay 29 becomes substantially torqueless, the biasing springs 35 and 36 act upon the gear rack 33 so as to provide the prime mover i with a fuel supply, so that it will operate at its maximum efllciency speed, and since the gear wheel 32 is connected through the shaft 3i to the contactor 21, it will cause the contactor 21 to oscillate in such a direction as to complete a circuit through the contact 23 to energize the field exciting winding I1, as described above. A stop 31 is arranged on the contact 23 so as to limit the movement of the contactor 21 when the torque of the relay 29 increases in the direction tending to open the throttle of the prime mover l beyond its maximum efliciency fuel intake position. For any operating condition represented by the curve 0-D, and d-e, the speed of the prime mover will tend to be higher than the maximum efficiency operating speed, so that the voltage of the auxiliary generator 2! will be higher than the voltage of the electric battery 5, and a current will tend to flow from the auxiliary generator 21 through the field exciting winding 28 to the battery 6. This current fiow will excite the field exciting winding 28 in such a direction that the torque developed by the relay 29 will be in a counterclockwise direction in Fig. l, and will act against the biasing force of the spring 35, thereby tending to close the prime mover throttle, and consequently, decrease the speed of the prime mover I, and also will tend to oscillate the contactor 21 in a counter-clockwise direction as shown. Such a movement of the contactor 21 will open the circuit between the contactor 21 and the contact 23, thereby opening the circuit of the field exciting winding l1 so that it becomes inoperative, and also completes a circuit between the contactor 21 and the contact 24. In this manner, the armature of the auxiliary generator 2i remains connected in series with the electric battery 6; and the field exciting winding 28 remains energized in the same direction as before. Thus, for all operating conditions of the main metadyne generator 2 represented by the curves ab and de, the field exciting winding I1 is inoperative, and the variator field excitin winding 10 is energized in accordance with the characteristic of the auxiliary metadyne exciter II as determined by the excitation provided by the variator field exciting winding Hi. This provides an energization of the main metadyne variator field exciting winding In by the auxiliary metadyne II which produces the desired secondary voltage-current characteristic of the main metadyne, as represented by the curve ab-fd--c in Fig. 5.

In Fig. 2 I have illustrated another embodiment of my invention which provides substantially the same characteristics as those of the system shown in Fig. 1, and the same reference numerals have been applied to corresponding elements in both figures. The characteristics of the system shown in this figure are illustrated in Fig. 8.

In this system, a substantially constant torque prime mover I, such as a Diesel engine, is arranged to drive a main generator 2 of the metadyne or armature reaction excitation type through a shaft 3. The main generator is provided with a set of primary brushes 4 and 5 connected across an electric battery 6, which is a substantially constant potential source of electrical power supply. A set of secondary brushes 1 and 8 are also associated with the armature 2 of the main generator, and are electrically displaced from the primary brushes 4 and 5, and supply an electrical load comprising motors 9 connected thereacross. The main generator 2 also is provided with a stationary member arranged to provide a path of low magnetic reluctance to the fluxes of the machine, and a field exciting winding I0 is arranged to excite magnetically the main generator and control its operating characteristics. This field exciting winding i0 is arranged to provide a component of magnetic excitation to the main generator in opposition to the secondary armature reaction set up by the secondary current fiowing through the armature between the secondary brushes 1 and 8. The operation of this type of variator field exciting winding is clearly explained in my U. S. Patent 1,987,417, January 8, 1935.

In order to stabilize the operation of the system shown in this figure, I provide a stabilizing field exciting winding 11a arranged to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter ll so as to vary the secondary current thereof, and therefore, to Vary the energization of the field exciting winding Ill of the main generator. This stabilizing field exciting winding l1a is connected across a stabilizing field exciting winding Illa arranged along the secondary commutating axis of the main generator 2. The excitation provided by these stabilizing field exciting windings may be in either direction, and the field exciting windings are arranged and.- connected so that the excitation produced along the secondary commutating axis of the metadyne exciter by the field exciting winding No is opposed to any component of excitation produced by any transient, alternating, or oscillating currents. Any change in the generator main field will induce a voltage in the main generator stabilizing field exciting winding Illa so that the current fiowing in this field exciting winding will be substantially 180 electrical degrees out of phase with the current producing the main generator excitation variation along its secondary axis. This induced current in the main generator stabilizing field exciting winding Illa will flow through the metadyne exciter stabilizing field exciting winding I'm in a direction so as to produce a component oi. excitation which will provide a variation in the excitation produced by the field exciting winding l8 opposed to the variations of the main excitation along the secondary commutating axis of the main generator produced by the alternating, oscillating, or transient currents. In this manner, such variations are efiectively neutralized or suppressed, and the stability of the system will be maintained. In this arrangement, currents induced in the exciter stabilizing field exciting winding l'la. also are fed back to the main generator field exciting winding la, and thus tend to neutralize transient, alternating, or oscillating variations in the secondary current of either of the two machines.

In the present arrangement, the energization of the variator field exciting winding I is provided by an auxiliary dynamo-electric machine II, also of the metadyne or armature reaction excitation type. This auxiliary metadyne exciter II is provided with a primary set of brushes l2 and i3 which are connected across the constant potential electric battery 8, and a secondary set of brushes l4 and 5 electrically displaced from the primary brush set and electrically connected across the terminals of the variator field exciting winding l8. As has been explained with respect to Fig. l, the voltage-current characteristic of the main metadyne generator 2 will be controlled by the excitation of the variator field exciting winding It, so that its characteristic will be substantially the same as the secondary voltagecurrent characteristic of the auxiliary metadyne dynamo-electric machine The auxiliary metadyne exciter II is provided with a field exciting winding 38 arranged to provide a component of excitation along the secondary commutating zone of the machine in opposition to the secondary armature reaction produced by the secondary current fiowing through the armature I between the brushes |5 and M. This field exciting winding 38 is arranged to be connected across the electric battery 6 in series with different resistances, so as to provide different predetermined constant values of excitation to the machine for different predetermined ranges of operation of the main metadyne generator 2. One of the terminals 39 of the field exciting winding 38 is connected to a terminal of the battery 8, and the other terminal 40 of the field exciting winding 38 isconnected to two electric contacts 4| and 42 of a voltage relay 43, and in series with a resistance 44 to a third electric contact 45 of an arcuately oscillatable relay 29. Another field exciting winding 48 is arranged to provide a component of magnetic excitation along the secondary commutating axis of the auxiliary metadyne exciter II in opposition to the excitation produced by the field exciting winding 38 and in accordance with an electrical characteristic of the main generator 2; namely, the secondary load voltage thereof. One of the terminals of this field exciting winding 46 is connected to the secondary brush 8 of the main generator, and the other terminal of this field exciting winding is connected to an electric contact 41 of the voltage-responsive relay 43, and to a second electric contact 48 of the oscillatable relay 28. A third field exciting winding I? also is arranged to provide a component of magnetic excitation along the secondary commutating axis or the auxiliary metadyne exciter H in opposition to ,the excitation provided by the field exciting winding 38, and is energized by an auxiliary dynamo-electric machine 2| in series with the battery 8. The auxiliary dynamo-electric machine 2| is excited by a shunt field exciting winding 23 directly connected across its terminals, and is driven in a predetermined speed relation to the speed of the main generator 2 and the prime mover by the shaft 8. This dynamo-electric machine is generally a regulator dynamo-electric machine, and the field exciting winding IT a regulator field exciting winding. The excitation of the field exciting winding I! by the regulator dynamo-electric machine 2| is arranged to maintain a substantially constant power output on the main generator I and the operation of such an excitation system is described in my U. S. Patent No. 2,038,384, April 21, 1936. One terminal of the field exciting winding I1 is connected to an electrical contact 23 of the relay 28, and the terminal 48 of the auxiliary dynamoelectric machine 2| is connected to another contact 24 of the relay 28, and the other terminal 50 of the dynamo-electric machine 2| is connected to a terminal of the battery 8.

The arrows on the field exciting windings I1, 38, and 48 indicate the relative directions of their excitation. As shown in this figure, an operating coil 5| of the voltage relay 43 is connected across the secondary brushes and 8 of the main metadyne generator 2, and this voltage-responsive relay is constructed so that it is biased to the position shown in Fig. 2, until a predetermined voltage is applied to the operating coil 5|, and for any voltage above this predetermined minimum voltage, the relay is actuated to its upper position. As shown, an upper contactor element 52 completes an electrical circuit between the contact 42 and a contact 54 when the relay is in its lower position, and is arranged w complete a circuit between the contact 4| and another contact 53 when the relay is actuated to its upper position. An electric contact 55 of the oscillatable relay 28 is connected directly to the contact 53 and in series with a resistance 55 to the contact 54. Furthermore, when the voltage-responsive relay is actuated to its upper position, as described above, an electrical contactor 58 is arranged to connect electrically the contact 41 to a contact 51, and the contacts 41 and 51 are disconnected when the relay 43 is in its lower position as shown in Fig. 2. The contact 57 is connected to an electrical contact 59 of the oscillatable relay 28, and is arranged to be electrically connected to another electric contact 80 of the relay 28 through a contactor 6| when the relay 28 is in the partially open throttle position shown in Fig. 2, and through the contact 80 to the secondary brush 1 of the main metadyne generator 2. Another contact 82 of the relay 28 also is connected to the secondary brush I in series with a resistance 83.

The operation of the oscillatable relay 28 is the same as that in Fig. 1, and as in that figure, the armature of the relay is connected across the battery 8 in series with a current limiting resistance 38. A shaft 3| mechanically connects the relay 28 to a contact arm which is composed of two electrically conductive elements 21 and 8| which are electrically insulated from each other by an insulating element 84. The direction and magnitude of the torque exerted by the rotatable member or the relay 28 is dependent upon the u excitation provided by a field exciting winding 28. One terminal of this field exciting winding 28 is connected to the battery 8, and its other terminal is connected through the contactor 2| and the contact 24 to the terminal 49 of the auxiliary dynamo-electric machine 2|, when the relay 29 is in the position shown in Fig. 2, and is connected through the contactor 21, the contact 23, and the field exciting winding i9 to the terminal 49 of the auxiliary dynamo-electric machine 2i when the relay 29 is in the full open throttle position shown by the dotted line in-Fig. 2. In this manner, the field exciting winding 28 is connected across the battery 8 in series with the dynamo-electric machine 21 under all operating conditions. As stated with respect to Fig. 1, the auxiliary dynamo-electric machine 2| is a, magnetically unsaturated dynamo-electric machine, the voltage of which varies directly with the operating speed of the machine, and is so constructed that when the speed thereof corresponds to the maximum efilciency speed of the prime mover i, the generated voltage across the terminals 49 and 58 of the auxiliary dynamoelectric machine 2| is exactly equal and opposite tothe terminal voltage of the battery 8. It is clear, therefore, that when the prime mover I operates at its maximum eificiency speed, there will be no current through the field exciting winding 28, as the voltage across this winding will be equal to the sum of the voltages across the terminal of the battery 8 and the dynamoelectric machine 2|, and since each of these voltages will be exactly equal and opposite in direction, there will be no voltage across the field exciting winding 28. Springs 35 and 38 are arranged to bias the throttle gear rack 33 to a position which provides the prime mover I with a fuel supply corresponding to the maximum emciency speed position. Thus whenever the relay 29 becomes torqueless, the springs 35 and 36 will act upon the throttle lever control gear rack 33 so as to urge the throttle to full open position. This actuation of the gear rack 33 will operate the gear wheel 32 which is secured to the end of the shaft 31, and will turn or oscillate the contact arm of the relay 29 to the full throttle position indicated by the dotted line in Fig. 2. This operating condition is indicated by the point I; in Fig. 8.

The field exciting windings i1, 38, and 46 of the auxiliary metadyne exciter H each are arranged to provide a predetermined component of excitation along the secondary commutating axis of the metadyne ll under predetermined operating conditions of the main generator 2. As has been explained above, the field exciting winding i1 is connected across the dynamo-electric machine 2! in series with the battery 8, and since the voltage of the dynamo-electric machine 2! is dependent upon the speed of the prime mover l, the energization of the field exciting winding 11 varies as a function of the speed of the prime mover I and of the main generator 2. The field exciting winding 38 is arranged to provide different predetermined constant components of excitation along the secondary commutating axis of the auxiliary metadyne H for different predetermined operating conditions of the main generator 2. The constant components of excitation provided by this field exciting winding depend upon the resistance in series with the winding 38 across the battery 6, and this resistance is varied by the position of the oscillatable relay 29 and the position of the voltage-responsive relay 43. The field exciting winding 48 is arranged to provide a variable component of magnetic excitation along the secondary commutating axis of the metadyne exciter II in accordance with the load voltage across the secondary brushes I and 8 of the main metadyne 2, and is arranged to provide different predetermined ranges of excitation for diiIerent predetermined load conditions on the main generator 2. These difierent ranges of excitation are obtained by changing the resistance in series with the field exciting winding 46 in response to difi'erent predetermined operating conditions of the main generator 2.

The automatic and inherent operation of the sys tem will be more readily understood by reference to Fig. 8 which represents the relation between the excitation of the main generator variator winding Ill and the secondary load voltage of'the main generator, and, since the secondary current of the main generator varies in accordance with variations in the excitation of the field exciting winding I8, the current ordinates shown in this figure also represent the relation of the secondary current to the secondary voltage of the main generator 2. Since the energization of the field exciting winding I0 is the only load connected across the secondary brushes of the auxiliary metadyne exciter H, its energization current is the same as the secondary current flowing through the secondary armature circuit of the auxiliary metadyne exciter. This secondary current of the auxiliary metadyne exciter II is controlled by the magnetic excitation along its secondary commutating axis, and this excitation is varied by the three field exciting windings i1, 38, and 48.

As has been stated with respect to Fig. 1, it is desirable that the secondary current and voltage of the main generator should not exceed a predetermined value. In Fig. 8 this maximum limiting safe secondary current is represented by the curve a--b, and at the operating point D the voltage-current relation is such that it is desirable that the power output should remain substantially constant to a maximum safe limiting voltage d, when the voltage should decrease rapidly, as represented by the curve de. Thus, the curve a--bjde represents a desirable generator characteristic for the main metadyne generator 2. In order to obtain such a characteristic, the relays 29 and 43 are arranged to vary the energization of the field exciting windings I1, 38, and 46 in response to predetermined operating conditions. The voltage responsive relay 43 is constructed so that when the secondary voltage of the main generator 2 is below the voltage b, the energization of the actuating coil is not sulficient to actuate the voltage-responsive relay 43 to its upper position. Furthermore, at the operating point b, any tendency for the load current to increase results in a reversal in the direction of current in the regulating field exciting winding I1 indicated by the difference between the ordinates of the curves t-b and p-b. This reversal of current in the field exciting winding l1 results in a reversal of current fiow through the relay field 28. The field exciting winding 28 is arranged so that under this condition, torque will be exerted by the rotatable member 29 upon the contact arm of the relay in a counter-clockwise direction, and this will operate the gear 32 and gear rack 33 so as to close partially the prime mover throttle. In this position of the voltage relay 43 and of the relay 29, the contact 23 is disconnected from the contactor 21, so that the field exciting winding I1 is deenergized. Furthermore, with this position of the voltage relay 43, the contactor 58 opens a circuit between the contacts 41 and 51, and the contactor 6 I on the operating arm of the relay 29 opens a circuit between the contact 48 and the contact 62 of this latter relay, so that the circuit of the field exciting winding 46 on the auxiliary metadyne H is open, and this winding also is deenergized. The terminal 38 of the field exciting winding 38 is connected to a terminal of the battery 6, and the terminal 48 of this field exciting winding is connected to the other terminal of the battery 8 in series with the resistance 58. This is the condition represented by the arrangement shown in Fig. 2, and the energizing current for the field exciting winding 38 fiows from the battery 6 through the winding 38 to the contact 42 of the relay 43,-through the contact 52 to the relay 54, through the resistance 58 to the contact 55, through the contactor 21 to the field exciting winding 28 of the relay 28, to the other terminal of the battery 6. The value of the resistance 56 is such that the resistance of this circuit will provide the field exciting winding 38 with an energization corresponding to the value 0a in Fig. 8. Since the battery 6 is a substantially constant source of electrical power supply, the excitation of the auxiliary metadyne exciter H is substantially constant as provided by the field exciting winding 38, so that the secondary current fiowing between the brushes l4 and I5 and through the field exciting winding II) also is substantially constant. This energization of the field exciting winding l8 controls the secondary current flowing between the secondary brushes and 8 of the main generator 2, and under these conditions, this secondary current is represented by the line ab in Fig. 8.

When operating along this portion ab of the generator characteristic, an increase in load results in a temporary slight decrease in prime mover speed, thereby slightly decreasing the generated voltage of the regulating dynamo-electric machine 2|. This results in a lowered counterclockwise torque in the relay 29, and thesprings 35 and 36 act to open the throttle of the prime mover and bring up its speed. This increase in speed increases the main generator voltage, thereby increasing the power delivered by the main generator to the load. When the secondary voltage Vz-s of the main generator 2 reaches the value b, the energizing current flowing through the coil 5| oi? the voltage-responsive relay 42 is sufiicient to actuate this relay to its upper position, thereby closing the circuit between the contacts 4| and 53, through the contactor 52 and the circuit between the contacts 41 and 51, through the contactor 58.

When operating at the point I), the speed of the prime mover is such that the voltage of the regulator dynamo-electric machine 2| will be exactly equal to the voltage of the battery 6, and no current will fiow therebetween, so that the field exciting winding 28 of the relay 29 will be deenergized, and this relay will be substantially torqueless. The springs 35 and 36 are so arranged that under these conditions, the throttle lever gear rack 33 is moved to the full open position of the throttle. This actuation of the gear rack 33 will cause the gear 32 and the actuating arm of the relay 29 to turn or oscillate in a clockwise direction, so that the contactor 6| will close the circuit between the contacts 48 and 62, and the contactor 21 will close the circuit between the contracts" and 24 through thefield exciting winding 28 and a terminal of the battery 8. This position of the relay 28 is indicated by the dotted line in Fig. 2 as the full throttle position. Under this condition, the terminal 39 of the field exciting winding 38 of the auxiliary metadyne exciter II is connected to a terminal of the battery 8, and the other terminal 40 of the field exciting winding 38 is connected to the other terminal of the battery 6 through the resistance 44. With this circuit, the energizing current of the field exciting winding 38 flows from the battery 6 through the resistance 44 tothe contact 45, through the contactor 21 and the relay field exciting winding 28 to the other terminal of the battery 6. The value of the resistance 44 is such that the resistance of this energizing circuit for the field exciting winding 38 will provide this field exciting winding with an energization respresented by the line pq in Fig. 8. The resistance of this field energizing circuit is less than the resistance of the energizing circuit of the field exciting winding 38 when connected in series with the resistance 56, so that the excitation produced by the field exciting winding 38 under these conditions is greater than when the prime mover is operated with a partially open throttle at low main generator voltages. Furthermore, the field exciting winding 46 is connected across the secondary brushes and 8 of the main generator 2, through the resistor 63,

the contact 62, the contactor 6| and the contact 48. The resistance 63 is such that the energization of the field exciting winding 46 will vary with the secondary voltage across the brushes 1 and 8, as shown by the line om in Fig. 8. Since the excitation produced by the field exciting winding 46 is opposed to the excitation produced by the field exciting winding 38 the excitation along the secondary commutating axis of the metadyne exciter I I produced by these two field exciting windings may be represented by the difference between the ordinates of the curves pq and o-m. This difierence is indicated by the line pb-c-dn. Furthermore, one terminal of the field exciting winding I1 is connected to the terminal 49 of the regulator dynamo-electric machine 2|, and the other terminal of the field exciting winding I! is connected to the contact 23 of the relay 29 through the contactor 21 and the field exciting winding 28 of the relay 29 to the battery 6 in series with the regulator dynamoelectric machine armature 2|.

As has been stated, at the point I) in Fig. 8, the voltage of the regulator dynamo-electric machine 2| will be exactly equal to the voltage of the battery 6, so that no current will fiow in this circuit, and therefore, the field exciting winding will not be energized at this point. If for any reason the load on the main generator 2 tends to increase, the prime mover tends to operate at a slightly decreased speed, so that the voltage of the regulator dynamo-electric machine 2| will be decreased and current will fiow from the battery 6 through the regulator dynamo-electric machine 2|, and the field exciting winding ll, so as to energize this field exciting winding. The field exciting Winding H is arranged to produce an excitation opposed to the excitation of the field exciting Winding 38 under these conditions, so that the net excitation along the secondary commutating axis of the exciter metadyne II is reduced, and the secondary current of the metadyne II, and consequently, the excitation produced by the field exciting winding I!) also is reduced, producing a corresponding reduction in the secondary current of the main generator 2. These conditions prevail whenever the prime mover operates with full open throttle, and the current-voltage characteristic of the main generator follows a constant power output characteristic, represented by the curve b-f-d in Fig. 8. The energization of the field exciting winding I! under these conditions is equal to the difference between the ordinates represented by the curve b-j-d and the curve b-c-d, so that the net excitation of the exciter metadyne I I along its secondary commutating axis, and consequently, the excitation produced by the main generator field exciting winding I4 follows a constant power hyperbolic characteristic represented "by the curve b-f-d in Fig. 8. The hyperbolic constant power generator characteristic represented by the curve b-j-d is such that the speed of the prime mover I corresponds to its maximum efiiciency speed, and any variation from this maximum efiiciency speedresults in a corresponding higher or lower generated voltage by the regulator dynamo-electric machine" 2|. This provides an increased or decreased excitation by the field exciting winding I1 and tends to maintain the secondary current of the metadyne exciter II, and consequently, the excitation of the field exciting winding II and the secondary current of the main generator 2, at such a value that the power developed by the main generator 2, and consequently, the load on the prime mover I remains substantially constant, and the prme mover I continues to operate at its maximum efiiciency speed at substantially constant torque.

' In order to obtain the voltage limiting characteristic of the generator 2 for the arrangement shown in Fig. 2, a largeramount of differential excitation by the field exciting winding 46 opposed to the excitation of the field exciting winding 38 must be produced than during the constant power operating conditions. when operating at these high secondary voltages, the operating coil SI of the voltage-responsive relay 53 is sufiiciently energized to actuate the voltage-responsive relay 4! in its upper posi-' tion. It the voltage and current of the main generator 2 reach the value indicated by the point d in Fig. 8, the speed of the auxiliary regulator dynamo-electric machine II is such that its voltage exactly equals the voltage of the battery 6 and substantially no current flows through the field exciting winding II of the metadyne exciter II. Any tendency of the secondary voltage of the main generator 2 to increase beyond the point (1 produces a reversal of current in the regulating field exciting winding I1, indicated in Fig. 8 by the difierence in the ordinates of the curves 41-11. and d-n. This reversal of current through the field exciting winding II results in a reversal of current through the relay field exciting winding 28, so that this relay exerts a torque in a counterclockwise direction against the biasing force of the springs 35 and 35, tending to close the prime mover throttle. This causes the contractor arm of the relay 29 to turn in a counter-clockwise direction and completes the circuits between the relay contacts as shown in Fig. 2. With this position of the voltage-responsive relay 43 and the relay 29, the contact 23 of the relay 2! is disconnected, and the field exciting winding I1 is deenergized, so that it no longer eiiects the excitation of the metadyne exciter II. Furtherwinding 24.

more, the contactor ll closes an electrical circuit between the contacts 41 and 51 so that the terminals of the field exciting winding 48 are connected through the contact 59, the contactor SI, and the contact GI, directly across the secondary brushes 1 and 8 o! the main metadyne generator 2. In this manner, the excitation provided by the field exciting winding 46 is greater than the excitation provided by this same field exciting winding when connected in series with the resistance Iii. The excitation produced by this field exciting winding under these conditions is represented by the line o --w in Fig. 8. Furthermore, the upper contactor 52 of the voltage-responsive relay 43 electrically connects the contacts H and 53; and the contactor 21 completes an electrical circuit between the contact 85 through the field exciting winding 28 of the relay 29, to the terminal 40 of the field exciting winding 34. In this manner, the field exciting winding 38 is connected across the battery 6 through the contact 4 I the contactor 52, the contact 55, the contactor 21, and the field exciting This energizing circuit of the field exciting winding 3! provides the highest excitation or its three circuit connections, and is indicated by the line r-s in Fig. 8. Since the excitation of the field exciting winding 46 is opposed to the excitation of the field exciting winding 38, the net or resultant excitation produced by these two field exciting windings is represented by the line r-d-e. Thus, for voltages of the main generator 2, higher than the value represented by the point (I, the voltagecurrent characteristic of the main generator follows the characteristic indicated by the curve de, and the secondary voltage of the main generator is limited to a predetermined sate operating value, as desired.

Referring to Fig. 9, I have shown another embodiment of my invention, and the same reference numerals as those oi! Figs. 1 and 2 are applied to corresponding elements in this figure. In this arrangement, the main generator 65 is a conventional dynamo-electric machine excited by a field exciting winding I energized by a coniormer metadyne exciter 66. The generator 85 is driven through a shaft 3 by a prime mover I, such as a Diesel engine, having a substantially constant torque characteristic, and supplies power to an electrical load including driving motors 9 connected across the brushes 61 and 68 of the generator. The driving motors may be used in various arrangements, such as for land vehicle, marine, machine tool, or similar drives. It is desirable that the prime mover I should operate at its maximum efiiciency speed, and since it is a substantially constant torque machine, it is desirable that the generator should have a substantially constant power output at the maximum efiiciency speed of the prime mover over the greater part of its operating range. Furthermore, it is also desirable that the generator have a characteristic which limits its maximum voltage and maximum current to safe limiting operating values. In order to obtain such a characteristic, 1'.- provide the metadyne exciter 66 with special field exciting windings energized so as to provide automatically and inherently the main generator field exciting winding II) with the desired characteristic. By operating the main generator 65' as a substantially unsaturated machine, its voltage-current characteristic bears a substantially direct linear relation to the excitation provided by its field exciting winding I0, and

therefore, to the secondary voltage-current characteristic of the metadyne exciter 68.

The energization of the field exciting windings of the metadyne exciter 66 is provided by the main generator 85 in accordance with certain of its operating characteristics and by two auxiliary dynamo-electric machines. One of these auxiliary dynamo-electric machines 89 is driven in a predetermined speed relation to the generator 65 through the shaft 3 by the engine I and is provided with self-excitation by a field exciting winding 10. This field exciting winding is arranged so that the auxiliary generator 69 operates as a saturated machine over the greater part of its operating range, and provides a substantially constant voltage source of electrical power supply. The other auxiliary dynamoelectric machine II also is driven in a predetermined speed relation to the speed of the main generator 65 and the prime mover- I, through the shaft 3 by the prime mover. A field exciting winding 12 is arranged to excite the auxiliary generator 1|, and is constructed so that it will operate as a magnetically unsaturated machine. This arrangement provides the auxiliary dynamoelectric machine H with a voltage characteristic which varies substantially as a direct linear func tion of the speed of the machine and varies over a wide range for small variations in speed. The field exciting winding 12 is connected across the brushes I3 and 14 of the auxiliary dynamo-electric machine ll, so that it still further insures relatively large voltage variations for small variations in the speed of the machine.

The metadyne exciter 66 is driven through the shaft 3 by the prime mover l, and is of the conformer type, provided with a pair of primary brushes l3 and I! which are short-circuited.- The operation of this type of metadyne dynamoelectric machine has been explained in my United States Patents 2,038,384, April 21, 1936; 2,073,525, March 9, 1937; and 2,079,465, May 4, 1937. The field exciting winding I of the main generator 65 is connected across secondary brushes l4 and I5 of the metadyne exciter 66, and therefore, the energization of this field exciting winding has the same characteristics as the secondary characteristics of the conformer metadyne 66. The characteristics of the secondary circuit of the conformer metadyne exciter 66 are determined by field exciting windings arranged to provide four components of magnetic excitation along the secondary commutating axis of the machine. The energizations of these field exciting windings are represented by the curves in Fig. 7. A field exciting winding is connected across the substantially constant potential saturated dynamoelectric machine 69, and provides a substantially constant component of magnetic excitation along the secondary commutating axis of the metadyne exciter in a given direction as represented by the arrow in Fig. 9. The curve 9-71. in Fig. '7 represents the relation between the ampere-turns energization of this field exciting winding 15 and the secondary voltage across the secondary brushes I4 and I5 of the exciter metadyne 66, or the voltage of the main generator 65, as these voltages bear a substantially direct linear relationship to each other. Another field exciting winding 16 is arranged to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter 66 in the same direction as the field exciting winding 15, as indicated by the arrow in Fig. 9, and is connected across the brushes 6! and 68 of the main generator. The component of energization provided by this winding varies as a linear function of the voltage of the main generator I, and therefore, of the secondary voltage of the metadyne exciter 66. This relationship is represented by the curve 0-40 in Fig. 7. The curve ol represents the relation of the sum of the energizations of the field exciting windings l5 and I! to the secondary voltage of the exciter metadyne l! or the voltage of the main generator 5. The curve oh-l represents the saturation curve of the metadyne exciter 66. Thus, if only the above field exciting windings are energized, the secondary voltage of the exciter and the voltage of the main generator will follow the curve 0-h-l and come to equilibrium at a value corresponding to the intersection point I of the,

curves oh-l and g-Z.

As has been stated, it is desirable that the main generator characteristic should have limiting voltage and limiting current values, and these operating conditions can be obtained by providing the generator with a drooping voltagecurrent characteristic. In order to obtain such a characteristic, I have arranged a field exciting winding 11 connected in series with the load circuit of the main generator 65 to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter in a direction opposed to the excitation of the field exciting windings l5 and I6, as indicated by the arrow in Fig. 9. In this manner, the energization of this winding 11 varies with the load current of the main generator 65, and the voltage of the main generator, and therefore, the secondary voltage of the metadyne exciter varies in such a manner that the excitation of the series field exciting winding 11 is exactly equal and opposite in direction to the difference between the sum of the excitations of the two field exciting windings IS-and l6 and the excitation necessary to produce the load voltage. Thus, on open circuit with no-load current, and therefore, no differential series field excitation, the secondary voltage of the metadyne exciter 66 and the voltage of the main generator 65 are built up to a value corresponding to the point I; that is, it will be equal to the value oe, and on short-circuit, with substantially no voltage across the brushes 6! and 68, the differential series excitation will be such as to buck down substantially all of the-excitation produced by the field exciting windings 15 and I6, and will be equal and opposite to the excitation og, and be represented by the point a in Fig. 7. For any intermediate load points, the differential excitation of the series differential field exciting winding TI is equal to the difference between the ordinates of the saturation curve oh-l and the curve g-l, and is represented by the curve ab--cde. In order to obtain a substantially constant maximum limiting current characteristic a-b, the resistance of the circuit of the field exciting winding 16 is made such that the curve olc coincides substantially with the portion of the saturation curve o-h/l representing the unsaturated characteristic of the metadyne exciter, so that the difference between the ordinates of the curves ohZ and gl is substantially constant for a wide range of voltage, and decreases rapidly beyond a predetermined value corresponding to the saturation point or knee in the saturation curve oh-l. Since the energization of the series differential field exload current 01 the main generator, the curve ab-c-de also represents the relation of the load current of the main generator to the main generator voltage and provides the main generator with a drooping voltage-current characteristic having the desired voltage and current limiting values.

To obtain maximum efiiciency from the prime mover I, it is desirable that the voltage-current characteristic of the main generator should be substantially hyperbolic; that is, that the output of the main generator should be substantially constant at the speed at which the prime mover operates at maximum efiiciency. This can be obtained by providing another component of magnetic excitation along the secondary commutating axis of the metadyne exciter 66, which is opposite in direction to the excitation of the field exciting windings 15 and 16; that is, in the same direction as that of the series differential field exciting winding 11. A field exciting winding 1! is arranged to provide a component of magnetic excitation in the direction indicated by the arrow in Fig. 9, and is arranged to be connected by an oscillatable relay 29 across the substantially constant potential of the saturated auxiliary dynamo-electric machine 69 in series with the variable voltage unsaturated auxiliary dynamoelectric machine II when the voltage of the unsaturated dynamo-electric machine H is equal to the voltage of the saturated dynamo-electric machine 69. The unsaturated dynamo-electric machine H is constructed so that its voltage is equal to that of the saturated dynamo-electric machine 69 when the load on the main generator corresponds to the values indicated by the points b and d which correspond to the maximum efiiciency speed of the prime mover l. The oscillatable relay 2! is provided with an armature connected across the auxiliary saturated dynamoelectric machine 69 through a current limiting resistor 30, and a field exciting winding 28 is arranged to provide an excitation thereto which varies in magnitude and direction with variations in the speed oi! the prime mover I. One terminal of the field exciting winding 28 is connected to a terminal of the saturated dynamoelectric machine 69 and the other terminal of the field exciting winding is connected to'an oscillatable contactor arm 21 which is mounted on a shaft 3! of the relay 29. This contactor 21 is arrangedto engage contacts 23 and 24 which are connected respectively through the field exciting winding 18 of the metadyne exciter to a brush 13 of the unsaturated dynamo-electric machine H, and directly to the brush I3 of the dynamo-electric machine H. When the voltages of the unsaturated dynamo-electric machine H and the saturated dynamo-electric machine 69 are equal, that is, at the points b and (I, no current flows through the field exciting winding 28 of the relay 28, and the relay is torqueless. Under this condition, a pair of biasing springs 35 and 36 are arranged to shift the throttle operating gear rack 34 to full open throttle position. This operation of the throttle operating gear rack rotates a gear wheel 32 which meshes with the gear rack 33 and is mounted on the shaft 3| of the oscillatable relay 29, and oscillates or turns the relay contactor arm 21 in a counter-clockwise direction from the position shown in Fig. 9. This completes an electrical circuit from the contact 24 through the contactor 21, through the relay field exciting winding 28, through the saturated dynamo-electric machine '3 and the unsaturat- -indicated by the arrow in the figure.

ed dynamo-electric machine H in series, and through the regulating field exciting winding ll. Under these conditions, if for any reason, load is added, the prime mover speed decreases slightly, and the voltage of unsaturated machine II also decreases, so that current fiows from the saturated dynamo-electric machine 89 through the unsaturated dynamo-electric machine 1| and energizes the regulating field exciting winding '|8 in the same direction as the series differential field exciting winding II, as

This excitation reduces the diflerential excitation required to establish equilibrium conditions, and consequently the-current in the series diflerential field -exciting winding 11 is decreased, so that the load current decreases and the prime mover speed increases again. This excitation of the regulating field exciting winding 18 is represented by the difference between the ordinates of the curve b--c--d and b-f-d, as this winding is energized in accordance with the difference in potential between the constant voltage of the auxiliary generator 69 and the variable voltage of the auxiliary generator "H which depends upon the speed of the prime mover l. The operation or this type of field exciting winding is described in my United States Patent 2,038,384, April 21, 1936.

For any operating condition represented by the curves ab and de the speed of the prime mover I will tend to be higher than the maximum efiiciency operating speed, so that the voltage of the unsaturated auxiliary dynamo-electric machine II will be higher than the voltage of the saturated dynamo-electric machine 63. Under these conditions a current will tend to fiow from the unsaturated dynamo-electric machine It through the field exciting winding 28 of the relay 29 to the saturated dynamo-electric machine 69. This current energizes the field exciting winding 28 in such a direction that the torque developed by the relay 29 is in a clockwise direction, and acts against the biasing force of the spring 36, thereby tending to close the prime mover throttle, and consequently, decreasing the speed of the prime mover l, and also tends to oscillate or turn the contactor 21 in a clockwise direction. Such a movement of the contactor 21 opens the circuit between the contactor 21 and the contact 24, thereby opening the circult of the field exciting winding 18 so that it becomes inoperative and completes a circuit between thecontactor 21 and the contact 23. In this manner, the unsaturated dynamo-electric machine H remains connected in series with the saturated dynamo-electric machine 69 and the field exciting winding 28 remains energized in the same direction as before. Under these conditions, the differential excitation of the series d fferential field exciting winding 1! follows the curves a,-b or ri -e, and thereby limits the secondary current or voltage, respectively, of the metadyne exciter 66. The main generator also will have a voltage-current characteristic represented by the curves ab and d-e, and its maximum current and voltage will thereby be limited to predetermined safe operating values as desired. In this manner the main generator 65 of conventional construction is provided with the desired operating characteristics by the metadyne exciter 66.

It is often desirableto obtain electrical load characteristics in an electrical power system without the use of electrical circuit changing, or

switching devices. In Fig. 10, I have shown another embodiment of my invention wherein the main generator is provided with the desired inherent load characteristics without the use of any circuit changing or switching devices. The same reference numerals as those of Figs. 1, 2, and 9 are applied to corresponding elements in this figure. This system is very similar to that of Fig. 9, and utilizes a conventional dynamoelectric machine 65 as the main generator. A prime mover I, such as a Diesel engine, having a substantially constant torque characteristic is arranged to drive the main generator 65 through a shaft 3, and the generator is supplied with excitation by a field exciting winding IE2, An electrical load comprising driving motors 9 is connected across the brushes 61 and 68 of the generator. For the reasons stated above, it is desirable that the generator should have a substantially constant power output at the maximum efiiciency speed of the prime mover over the greater part of its operating range, and that the generator characteristic should limit the maximum voltage and maximum current to safe operating values. In order to obtain such a characteristic, I provide a metadyne exciter 66 with special field exciting windings energized so as to provide inherently and automatically the main generator field exciting winding In with the desired excitation. By operating the main generator 65 as a substantially unsaturated machine, its voltagecurrent characteristic bears a substantially direct linear relation to the excitation provided by its field exciting winding l0, and therefore, to the secondary voltage-current characteristic of the metadyne exciter 66.

As in Fig. 9, the energization of the field exciting windings of the metadyne exciter 66 is provided by the main generator 65 in accordance with certain of its operating characteristics in conjunction with two auxiliary dynamo-electric machines and a battery 6, which is arranged to provide a substantially constant potential source of electrical power supply. The metadyne exciter 66 is of the conformer type, and is provided with a pair of primary brushes l2 and I3 which are short circuited, similar to the exciter shown in Fig. 9. The field exciting winding III of the main generator 65 is connected across a pair of secondary brushes H and I5 of the metadyne exciter 66, and therefore, the energization of this field has the same characteristics as the secondary characteristics of the conformer.

metadyne 66. These secondary circuit characteristics are determined by field exciting windings arranged to provide four components of magnetic excitation along the secondary commutating axis of the machine. The energizations of these field exciting windings are represented by the curves in Fig. 13. A field exciting winding 15 is connected across a substantially constant potential electric battery 6, and provides a substantially constant component of magnetic excitation along the secondary commutating axis of the metadyne exciter in a given direction, as represented by the arrow in Fig. 10. The curve gh in Fig. 13 represents the relation between the ampere-turns energization of the field exciting winding I5 and the secondary voltage across. the secondary brushes I4 and I5 of the metadyne exciter 66, or the voltage of the main generator 65. Another field exciting winding 16 is arranged to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter in the direction indicated by the arrow in Fig. 10, and is connected to provide a component of excitation which varies with the voltage of the main generator or the secondary metadyne voltage. To obtain this result, it is connected across the brushes 61 and 68 of the main generator. The component of energization provided by this field exciting winding varies as a linear function of the voltage of the main generator 65, and therefore, of the secondary voltage of the metadyne exciter 66. This relationship is represented by the curve 0-7:: in Fig. 13, and the curve g-l represents the relation of the sum of the energizations of the field exciting windings 15 and 16 to the secondary voltage of the metadyne exciter 66, or the voltage of the main generator 65. The curve 0-hl-:c represents the saturation curve of the metadyne exciter 66, and therefore, if only the above field exciting windings are energized, the secondary voltage of the exciter, and the voltage of the main generator will follow the curve o-h-lx and come to equilibrium at a value corresponding to the intersection point I of the curves ohl-:c and g-l.

As stated above, it is desirable that the main generator characteristic should have limiting voltage and limiting current values, as well as, a substantially constant power characteristic over the greater part of its operating range. In order to obtain such a characteristic, I have arranged a field exciting winding 11 connected in series with a load circuit of the main generator 65 to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter in a direction opposed to the excitation of the field exciting windings I5 and 16, as indicated by the arrow in Fig. 10. In this manner, the energization of this field exciting winding varies with the load current of the main generator 65, and the voltage of the main generator and, therefore, the voltage of the metadyne exciter, varies in such a manner that the excitation of the series field exciting winding 11 is equal and opposite in direction to the difi'erence between the sum of the excitations along the secondary commutating axis of the metadyne 66 in the direction of the excitations produced by the field exciting windings l5 and 16, and the excitation necessary to produce the load voltage. This load voltage is determined by the saturation of the curve of the machine.

In order to obtain inherently the desired characteristics, I provide a special dynamo-electric machine which is provided with a field exciting winding connected directly across the constant potential battery 6. This field exciting winding provides a substantially constant component of magnetic excitation to the dynamoelectric machine I! in the direction indicated by the arrow in Fig. 10, and is arranged to saturate substantially the dynamo-electric machine 19, so that under normal operating conditions, if this winding alone is energized, the dynamo-electric machine 19 will operate at about its saturation point, which is represented by the knee in its saturation curve. In Fig. 12, curve f-o-b-c illustrates the saturation curve for the dynamoelectric machine 19, and the point b on this curve represents the saturation point, and therefore, the condition under which the dynamo-electric machine 19 operates when only the field exciting winding 80 is energized. I provide an auxiliary dynamo-electric machine 2| which is excited by a field exciting winding 22 connected across its own terminals, so that it is a self-excited ma- 75 chine, and the field exciting winding 22 is arranged so that the dynamo-electric machine 2| operates as an unsaturated machine. In this,

manner, the voltage across the brushes oi the dynamo-electric machine 2| varies considerably with small variations in the speed of this machine. In order to utilize the dynamo-electric machine 2| as a regulator, it is driven in a predetermined speed relation to the speed of the engine I through the shaft 8 by the prime mover battery 8 when the speed 01' the prime mover I corresponds to its maximum efilciency speed. Under these conditions, no current flows through the field exciting winding 8| of the auxiliary dynamo-electric machine 18, and the excitation of this machine corresponds to the point b in Fig. 12. It for any reason the speed of the prime mover decreases, as when additional load is placed on the main generator 85, the voltage of the auxiliary dynamo-electric machine 2| also decreases, so that current fiows from the battery 8 through the field exciting winding 8| to the dynamo-electric machine 2|. The field exciting winding 8| is arranged so that when current flows from the battery to the dynamo-electric machine 2|, when the voltage of the dynamoelectric machine 2| is lower than that. of the battery 8, the excitation produced by the field exciting winding 8| is opposite in direction to that provided by the field exciting winding 88. Under this condition, the dynamo-electric machine 18 operates as an unsaturated dynamo-electric machine. This range of operationis represented by the curve f--b in Fig. 12. The curve ob illustrates the operation of the dynamo-electric machine 19 when the excitation provided by the field exciting winding 88 is greater than the excitation provided by the field exciting winding 8|, and the curve of represents the characteristic of this machine when the excitation produced by the field exciting winding 88 is less than the excitation produced by the field exciting winding 8|. If for any reason the speed of the prime mover I tends to increase above its maximum efiiciency speed, as when load is reduced or removed from the main generator 85, the voltage generated by the dynamo-electric machine 2| becomes greater than that 01' the constant potential battery 6, and current fiows from the dynamo-electric machine 2| through the field exciting winding 8| to the battery 8. Under this condition, the excitation produced by the field exciting winding 8| is in the same direction as that of the field exciting winding 88, and since the field exciting winding 88 substantially saturates the dynamo-electric machine I8, the voltage of this machine varies only slightly, due to the increased excitation produced by the field exciting winding 8|. This is represented in Fig. 12 by the portion b-c of the saturation curve o--bc.

A field exciting winding 82 is arranged to produce a component of magnetic excitation along the secondary commutating axis of the conformer metadyne exciter 86, and is connected across the brushes of the auxiliary dynamoelectric machine 18. In this manner, the field exciting winding 82 is energized in accordance with the resultant excitation produced by the field exciting windings 88 and 8| upon the auxiliary dynamo-electric machine When the field exciting winding 8| is not energized, the excitation produced by the field exciting winding 82 corresponds to the value e--b, Fig. 12, and this is represented in Fig. 13 by the ampere-turns om. The curve mrn represents the constant excitation produced by the field exciting winding 82 in the direction indicated by the arrow in Fig. corresponding to the energization of the field exciting winding by the auxiliary dynamoelectric machine 18, due to the excitation produced by the field exciting winding 88. Thus, the constant component of excitation along the secondary commutating axis of the metadyne exciter 86 comprises two components, that component produced by the field exciting winding I5 and represented in Fig. 13 by the curve g-h, and

another component produced by the field exciting winding 82,-and represented by the curve m-n. Thus, it the field exciting winding 8| of the auxiliary dynamo-electric machine remains deenergized, the metadyne exciter 86 will have a drooping current voltage characteristic similar to that of the metadyne exciter in the system illustrated in Fig. 9, and which can be represented in Fig. 13 by the curve i-bc-d-7'.

The ordinates of this curve correspond to the difference inthe ordinates between the saturation curve 0--h--Z-:c and the curve mu-w, which represents the sum of the component excitations in the same direction in the system of Fig. 10. As explained above, the field exciting winding 8| is deenergized only when the prime mover operates at its maximum efiiciency speed, and this corresponds in Fig. 13 to the points b and d, and in Fig. 12 to the point D. In order to obtain the desired current and voltage limiting characteristics and the constant power characteristic, the energization of the field exciting winding 82 is varied by the energization of the field exciting winding 8|. As has been explained above, these characteristics are obtained by varying the component of excitation provided to the metadyne exciter 68 by the field exciting winding 82. This component of excitation is represented in Fig. 13 by the curve pq-1's-t, and the portions Hand s-t of this curve represent the excitation of the field exciting winding 82 when the speed of the prime mover is slightly higher than the maximum eificiency speed and corresponds to the operation of the auxiliary dynamo-electric machine 18 as a saturated machine. The portion q-r-s of this curve represents the excitation produced by the field exciting winding 82 when the auxiliary dynamo-electric machine 18 operates as an unsaturated dynamo-electric machine, that is, when the excitation of the field exciting winding 8| opposes the excitation of the fieldexciting winding 88 due to the fact that the voltage of the auxiliary dynamo-electric machine 2| is less than the voltage of the constant potential battery 6. This condition occurs when the load on the prime mover is increased, so that its speed tends to fall below its maximum efiiciency speed. Thus, the sum of the excitations produced by the field exciting windings 15, I6, and 82, all of which provide excitation in the same direction along the secondary commutating axis of the metadyne exciter 68 is represented by the curve puvwa: in Fig. 13. The ordinates of this curve represent the sum of the ordinates of the curves olc, gh,

and p-q--r-st. In this manner, the substantially constant excitation of the metadyne exciter 66 is slightly increased over the value --m to the value o-p, but this increase is very slight, I and is due only to the slight increase provided by the field exciting winding 8| when the auxiliary dynamo-electric machine 16 operates as a saturated machine. Thus, the energization of the series difl'erential field exciting winding TI will 16 be equal and opposite to the excitation represented by the diiIerence in the ordinates of the saturation curve 0h-Z-w and the curve p-u-v-w-x, representing excitation required by saturation or the exciter 66 and the sum of the ll excitations produced by the field exciting windings 16, I6, and 62, respectively. This energization of the series field exciting winding 'I'I will result under all operating conditions, as the current in this field exciting winding will vary in U such a manner that the excitation of this field exciting winding 11 will buck down the total excitation of the metadyne exciter 66 to a net value corresponding to the voltage required for that particular load, as indicated by the satu- 3' rated curve oh-l-:r. In Fig. 13, the curve a;ujze represents the energization of the series diilerential field exciting winding I1, and therefore, represents the relation of the current through this field exciting winding to the sec- 86 ondary voltage of the metadyne exciter 66, or the voltage of the main generator 65. Thus, it is seen that the inherent voltage-current characteristic of the main generator 66 is represented in Fig. 13 by the curve a'-1/-fz-e. In this manner, whenever the load on the main generator 65 is such that the speed of the prime mover I tends to increase over its maximum eiiiciency speed, the field exciting windings 15, I6, and 82 on the metadyne exciter 66 tend to limit the secondary current or voltage of the metadyne exciter 66, and therefore, of the main generator 65. This operation is represented in Fig. 13 by the portions ay and z-e of the curve ay-fze, and the points 1 and 2 represent the conditions when u the voltage of the auxiliary dynamo-electric machine 2I is equal to the voltage of the constant potential battery 6, and therefore, when the prime mover I is operating at its maximum efilciency speed. Whenever the load on'the main I. generator 65 tends to increase, the speed of the prime mover I will tend to decrease, and the excitation of the field exciting winding 82 will be reduced, so that the load will become less, and the speed of the prime mover I will again increase 55 to substantially the maximum efilciency speed. The operation of this type of winding is described in my United States Patent 2,038,384, April 21, 1936. Inthis manner, the main generator '65 will have a substantially constant power output .0 characteristic ;uf--z, which corresponds substantially to the hyperbolic relation represented by the curve b-fd. I

As in Figs. 1, 2, and 9, I provide a throttle con trolling oscillatable relay 29, the armature of it which is connected across the substantially constant potential battery 6 in series with a current limiting resistor 36, and which is provided with a field exciting winding 26 connected in series with the unsaturated auxiliary dynamo-electric machine 2I and the battery 6. A shaft 3| connects the relay 29 to a gear wheel 32 which meshes with the gear rack 23. As has been explained with respect to the above-mentioned figures, when the speed of the prime mover I corresponds to its maximum efiiciency speed. no current flows through the field exciting winding 28, as the voltage of the auxiliary dynamo-electric machine 2I and the battery 6 are exactly equal and opposite, and the relay 29 is torqueless. Under this condition, a pair of biasing springs 35 and 36 actuate a throttle controlling gear rack 33 to the full open throttle position. Furthermore, whenever the load on the prime mover I is lessened, with the consequent increase in speed of the prime mover above the maximum eiliciency speed, the voltage of the auxiliary dynamo-electric machine 2I becomes greater than that of the constant potential battery 6, and current fioyvs through the field exciting winding 26 01 the relay 29 in such a direction that the relay 26 exerts a torque in a counter-clockwise direction in the figure. Thus, when the load on the prime mover I is lessened, the relay 29 exerts a counterclockwise torque which turns or rotates the gear wheel 32 in a counter-clockwise direction, and tends to partially close the throttle of the prime mover I and decreases the power developed by the prime mover. In this manner, the system disclosed in Fig. 10 inherently provides the desired operating charactertistics Without the use of cir- 5 cult changing or switching devices.

In Fig. 11 I have illustrated another power systern wherein the desired electrical load characteristics are obtained inherently and automatically without the use of electric circuit changing or 30. switching devices somewhat similar to the system illustrated in Fig. 10. The same reference numerals as those of Figs. 1, 2, 9, and 10 are applied to corresponding elements in this figure. As'shown in Figs. 9 and 10, this system utilizes a conventional dynamo-electric machine 65 as the main generator. A prime mover I, such as a Diesel engine, having a substantially constant torque characteristic, is arranged to drive the main generator 65 through a shaft 3, and the 40 generator is supplied with excitation by a field exciting winding I0. An electrical load comprising driving motors 9 is connected to the brushes 61 and 68 of the generator. As stated with respect to the other systems, it is desirable that the generator should have a substantially constant power output over the greater part of its operating range, and that the generator characteristic should limit the maximum current and voltage to safe operating values. In 50, order to obtain such a characteristic, I provide a metadyne exciter 83 with special field exciting windings energized so as to provide the main generator field exciting winding III with the desired excitation. By operating the main gen- 56 erator 65 as a substantially unsaturated machine over a portion of its operating range, its voltagecurrent characteristic bears a substantially linear relation over this operating range to the excita-. tion provided by its field exciting winding I6, and 00 therefore, to the secondary voltage-current characteristic of the metadyne exciter 63.

The excitation of the field exciting windings of the metadyne exciter 83 is provided by the main generator 65 in accordance with certain of 65 its operating characteristics in conjunction with a regulator field exciting winding energized in accordance with the speed of the machine and a field exciting winding arranged to provide a substantially constant component of excitation.

The metadyne exciter 63 is of the conformer type and is provided with a pair of primary brushes I2 and I3 which are short-circuited through a small resistance provided by a field exciting winding 64 arranged on an oscillatable dynamo-electric re- 7 aaoas'u lay II. The field exciting winding N of the main generator 88 is connected across a pair of secondary brushes I4 and I! of the metadyne exciter 88, and therefore, the energization of this field exciting winding has the same characteristics as the secondary characteristics of the conformer metadyne exciter 83. These secondary circuit characteristics are determined by field exciting windings arranged to provide four components of magnetic excitation along the secondary commutating axis of the machine. The energizations and excitations of these field exciting windings are represented by curves in Fig. 6. A field exciting winding 15 is connected across a substantially constant potential electric battery 6 and provides a substantially constant component of excitation along the secondary commutating axis of the metadyne exciter 88 in a given direction as represented by the arrow in Fig. 11. The curve yh in Fig. 6 represents the relation between the ampere-turns of energization of the field exciting winding 15 and the secondary voltage across the secondary brushes II and I5 of the metadyne exciter 88 or the voltage of the main generator 85. Another field exciting winding 18 is arranged to provide a component of magnetic excitation along the secondary commutating axis of the metadyne exciter 83 in the direction indlcated by the arrow in Fig. 11. This field exciting winding is connected to provide a component of excitation which varies with the voltage of the main generator or the secondary metadyne exciter voltage and is connected across the brushes 61 and 68 of the main generator. The component of energization provided by this field exciting winding varies as a linear function of the voltage of the main generator 65, and therefore, of the voltage of the metadyne exciter it This relationship is represented by the curve o-k in Fig. 6, and the curve y--l represents the relation of the sum of the energizations of the field exciting windings 15 and 18 to the secondary voltage of the metadyne exciter 83 or the voltage of the main generator 85. The curve o-hl represents the saturation curve of the metadyne exciter 83, and therefore, if only the above field exciting windings are energized, the secondary voltage of the metadyne exciter, and therefore, the voltage of the main generator will follow the curve o'-h-l and come to equilibrium at a value corresponding to the intersection point 1 of the curves o-h-l and -1.

In order to obtain a generator characteristic having a limiting voltage and limiting current, I have arranged a field exciting winding 11 connected in series with the load circuit of the main generator 85 to provide a component of magnetic excitation along the secondary comutating axis of the metadyne exciter 83, in a direction opposite to the excitation of the field exciting windings l5 and 18 as indicated by the arrow in Fig. 11. In this manner, the energization of this field exciting winding varies with the load current of the main generator, and therefore, the voltage of the metadyne exciter and the voltage of the main generator, vary in such a manner that the excitation of the series field exciting winding 11 is equal and opposite in direction to the difierence between the sum of the excitations along the secondary commutating axis of the metadyne exciter 88 in the direction of the excitations produced by the field exciting windings l5 and I8 and the excitation necessary to produce the load voltage for any given load current. This load voltage is determined by the saturation curve oi. the machine.

In order inherently to obtain the desired characteristics, I provide an auxiliary dynamo-electric machine 2| which acts as a speed regulator and I is excited by a field exciting winding 22 connected across its own terminals, so that it is a selfexcited machine. The field exciting winding 22 also is arranged so that the dynamo-electric machine 2| operates as an unsaturated machine. 10 Thus, the voltage across the brushes of the dynamo-electric machine 2| varies considerably with small variations in the speed of this machine. In order to utilize the dynamo-electric machine 2| as a speed regulator, it is driven in II a predetermined speed relation to the speed of the engine I through the shaft 3 and is connected across a field exciting winding I'I arranged to pro vide a component of magnetic excitation along the secondary commutating axis of the meta- M dyne exciter 83 and is connected in series with the constant potential battery 8. The dynamoelectric machine 2| and its field exciting winding 22 are constructed so that the voltage generated by the dynamo-electric machine is exactly equal 88 and opposite to that of the electric battery 8 when the speed of the prime mover corresponds to its maximum efliciency speed. Under these operating conditions, no current flows through the field exciting winding l1 and the excitation provided by this field exciting winding under these conditions corresponds to the points I) and d in Fig. 6. If for any reason the speed of the prime mover decreases, as when additional load is placed on the main generator 85, the voltage of 88 the auxiliary dynamo-electric machine 2| also decreases, so that current flows from the battery 8 through the field exciting winding H to the dynamo-electric machine 2|, and the excitation produced by the field exciting winding I! under 40 these conditions is opposite in direction-to that produced by the field exciting windings l5 and 18. If, on the other hand, the load in the prime mover decreases beyond that developed by the prime mover, the speed of the set tends to in- 45 crease and the voltage of the auxiliary dynamoelectric machine 2| becomes greater than that of the battery, and current flows from the auxiliary 2| through the field exciting winding II to the battery 6. Under these conditions, the 50 field exciting winding provides a component of magnetic excitation in the same direction as the flux produced by the field exciting windings I5 and 16. The operation of this type of field exciting winding does not form part of this in- 55 vention, and is covered by my U. S. Patent 2,038,384, April 21, 1936. The excitation produced by the regulator field exciting winding I1 is represented by the difference in the ordinates between the curves 11-0-4 and bfd in Fig. 6. .0 Thus, the main generator 65 is provided with an excitation by the field exciting winding III which varies in accordance with the curve ibf-d-j in Fig. 6. Since it is not usually desirable to operate large dynamo-electric machines as un- 65 saturated machines throughout their practical range of operation as unsaturated machine over their entire range of operation, saturation of such machines will tend to vary the operating characteristics from that represented by the [0 curve i-b-f-d-a, although such variations will generally be very small, and the resultant characteristic may be represented by the curve ab--fd-e.

Since the prime mover is a substantially con- 1;

stant torque machine operating at a substantially constant speed for any given throttle condition, its power will not be sumciently utilized if the load on the main generator 88 does not remain substantially constant at full open throttle. It is desirable, therefore, that the throttle opening be varied in accordance with the load on the main generator 88, and this may be done by controlling the throttle position of the engine I. This control is provided by operation of a gear rack 33 which is biased by a spring 38 to full open throttle position. A gear wheel 32 mounted on a shaft 3| engages the gear rack 33 and is arranged to vary the position 01' the throttle under diflerent operating conditions. The gear wheel 32 is driven by another gear wheel 86 through a worm gear 87 by the oscillatable dynamo-electric relay 88 or another similar dynamo-electric relay 88. The armatures of the relays 88 and 88 are mounted on a shaft 88 which carries a worm gear 8'! and the field exciting windings of these two relays are arranged to provide excitation to the two relays so that the torques of the rotatable elements of the relays tend to turn the worm gear 81 in opposite directions. The armatures 88 and 88 of the two relays are connected in series with a current-limiting resistor 80 across the electric battery 8. The field exciting winding 84 of the relay 88 is connected in series with the primary brushes of the auxiliary metadyne exciter 83, and therefore, provides an excitation to the relay 88 in accordance with the primary current flowing in the primary circuit of the metadyne exciter. In this manner, the energization of the field exciting winding 84 will be proportional to the secondary voltage oi the auxiliary metadyne 83 as long as the metadyne operates as an unsaturated machine, but if the metadyne 83 becomes saturated, the primary current increases rapidly for slight increase in secondary voltage. This is represented in Fig. 6 by the curve 1' 1 A second field exciting winding 9| is arranged on the relay 88 to provide an excitation thereto in opposition to the excitation provided by the field exciting winding 84, and is connected across the terminals of the main generator 88. This provides a component of excitation to the relay 88 which varies in accordance with the voltage of the main generator 68, and therefore, varies substantially in accordance with the secondary voltage of the metadyne exciter 83. The excitation provided by the field exciting winding 8| is represented by the curve 0-s-m in Fig. 6, and the resistance of the field exciting winding 8| is made such that the excitation produced by this field exciting winding is substantially equal and opposite to that produced by the field exciting 84 as long as the metadyne exciter 83 operates as an unsaturated machine. In this manner, the

auxiliary dynamo-electric relay 85 is substantially torqueless for all voltages of the main generator 88 below a voltage corresponding to the point (I in Fig. 6, as it has very little excitation below this point as represented by the diiIerence in the ordinates between the curves 0r and 0-42. Beyond the point d, the excitation of the relay 88 increases very rapidly, and the excitation of this machine under these conditions corresponds to the difference in the ordinates between the curves r-n and s-m. The relay 88 and the biasing spring 38 are so constructed that the torque developed by the relay 88 under the excitation s-r is :ufilcient to close partially the T throttle of the prime mover l, and as the speed .01 the prime mover i tends of the prime mover l tends to increase from d to e, the torque of the relay 88 increases from r to m-n. thereby closing the prime mover throttle and decreasing the power developed by the engine i. 8

Furthermore, when the generator 88 operates along that portion 01' its characteristic which is represented by the curve 0-12 in Fig. 6, the speed maximum efiiciency speed it the generator 88 does not utilize all the power developed by the prime mover. Under these conditions, it was desirable that the prime mover throttle should'be partially closed. I provide a field exciting winding 92 arranged to excite the dynamo-electric machine relay 88 to provide a torque to this relay which varies in accordance with the load current of the main generator. This field exciting winding 92 is, therefore, connected in series with the load circuit oi. the main generator 88. The relay 88 and the throttle biasing spring 38 are so constructed that the torque developed by the relay is not suflicient to operate the throttle controlling mechanism for any value of load current below that represented by b in Fig. 6. However, when the load current increases above the value b along the characteristic represented by the curve the relay 88 develops torque in such a'direction that it tends to close the prime mover throttle against the tension of the biasing spring 38, and reduces the power developed by the prime mover I. Thus, whenever the prime mover I tends to develop more power than is required by the load on the generator 88, the throttle controlling mechanism tends to vary the throttle opening and controls the power developed by the prime mover to that required by the load on the main generator 88. The changes in speed produced by variations in throttle position of the prime mover also tend to produce slight changes in the operating characteristic of the main generator 88 and these slight changes coupled with saturation variations in the characteristic of the main generator 88 result in the differences between the operating characteristic abfde and that represented by the curve ibfd7. Thus. it is seen that I have provided a power system without electric circuit changing or interrupting devices wherein a conventional generator is provided with an operating characteristic having current and voltage limiting portions and a substantially constant power portion over its main operating range.

While I have illustrated and described particular embodiments 01' my invention, modifications thereof; will occurto those skilled in the art. I desire it to be understood, therefore, that my invention is not to be limited to the particular arrangements disclosed, and I intend in the appended claims to cover all modifications which do not depart from the. spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent 01 the United States, is:

1. An excitation system for a dynamo-electric machinev including a field exciting winding, dynamo-electric means arranged to energize said field exciting winding, and means for varying the energization provided by said dynamo-electric means to regulate the power output of the dynamo-electric'machine to a substantially constant value within predetermined limits of electrical potential and current and to limit the electrical potential and current of said dynamo-electric machine to predetermined maximum values.

to be higher than its 10 2. An excitation system for a dynamo-electric machine including a field exciting winding, dynamo-electric means arranged to energize said field exciting winding, and means for varying automatically the energization provided by said dynamo-electric means to regulate the power output of the dynamo-electric machine to a substantially constant value within predetermined limits of electrical potential and current and to limit the electrical potential and current 01' said dynamo-electric machine to predetermined maximum values.

3. An excitation system for a dynamo-electric machine including a field exciting winding, an auxiliary dynamo-electric machine arranged to energize said field exciting winding, means including a second field exciting winding for varying the energization provided by said auxiliary dynamo-electric machine to regulate inherently the power output of said first-mentioned dynamo-electric machine to a substantially constant value within predetermined limits of electrical potential and current, and means for varying the energization provided by said auxiliary dynamoelectric machine to vary inherently the power output of said first-mentioned dynamo-electric machine when the electrical potential or current thereof tends to exceed said predetermined electrical potential or current.

4. An excitation system for a dynamo-electric machine including a field exciting winding, dynamo-electric means arranged to energize said field exciting winding, means for varying automatically the energization provided by said dynamoelectric means to regulate the power output oi. the dynamo-electric machine to a substantially constant value within predetermined limits of electrical potential and electriccurrent and to limit the electrical potential and current of said dynamo-electric machine to predetermined maximum values, and means dependent upon variations in an electrical characteristic'of said dynamo-electric machine for varying the energization provided by said dynamo-electric means so as to oppose said variations of said electrical characteristic.

5. An excitation system for a dynamo-electric machine including a field exciting winding, an

7 auxiliary dynamo-electric machine arranged to energize said field exciting winding, means including a second field exciting winding for varying the energization provided bysaid auxiliary dynamo-electric machine to regulate the power output of said first-mentioned dynamo-electric machine to a substantially constant value within predetermined limits of electrical potential and current, and means including a third field exciting winding for varying the energization provided .by said auxiliary dynamo-electric machine to vary the power output of said first-mentioned dynamo-electric machine when the electrical potential or current thereof tends to exceed said predetermined electrical potential or current.

6. An excitation system for a dynamo-electric machine including a field exciting winding, an auxiliary dynamo-electric machine arranged to energize said field exciting winding, means including a second field exciting winding for varying the energization provided by said auxiliary dynamo-electric machine to regulate automatically the power output of said first-mentioned dynamo-electric machine to a substantially constant value within predetermined limits of electrical potential and current, and means including a third field exciting winding for varying the energization provided by said auxiliary dynamoelectric machine to vary automatically the power output of said first mentioned dynamo-electric machine when the electrical potential or current thereof tends to exceed said predetermined electrical potential or current. v

'7. An excitation system for a main dynamoelectric machine including a field exciting winding therefor, a metadyne dynamo-electric machine provided with a rotatable member havin a commutator arranged to energize said main dynamo-electric machine field exciting winding, said metadyne dynamo-electric machine bein provided with a primary brush set and asecondary brush set electrically displaced from said primary brush set and arranged to provide a primary commutatingaxis and a secondary commutating axis respectively for said rotatable member, a field exciting winding for-said metadyne dynamo-electric machine arranged to provide a component of magnetic excitation along the secondary commutating axis thereof dependent upon an electrical characteristic of said main dynamo-electric machine, means for providing a substantially constant component of magnetic excitation along the secondary commutating axis of said metadyne dynamo-electric machine, means dependent upon the speed of said main dynamo-electric machine for maintaining substantially constant power output thereof between predetermined values of electrical potential and current, and means for controlling a component of magnetic excitation along the secondary commutating axis of said metadyne dynamo-electric machine to limit the secondary current and the secondary voltage thereof to a predetermined maximum value.

8. An excitation system for a main dynamoelectric machine including a field exciting winding therefor, a metadyne dynamo-electric machine provided with' a rotatable member havin a commutator arranged to energize said main dynamo-electric machine field exciting winding, said metadyne dynamo-electric machine being provided with a primary brush set and a secondary brush set electrically displaced from said primary brush set and arranged to provide a primary commutating axis and a secondary commutating axis respectively for said rotatablemember, a field exciting winding for said metadyne dynamo-electric machine arranged to provide a component of magnetic excitation along the secondary commutating axis thereof dependent upon an electrical characteristic of said main dynamo-electric machine, means for providing a substantially constant component of magnetic excitation along the secondary commutating axis of said metadyne dynamo-electric machine, means dependent upon the speed of said main dynamo-electric machine for maintaining substantially constant power output thereof between predetermined values of electrical potential and current, and means for controlling a component of magnetic excitation along the secondary commutating axis of said metadyne dynamo-electric machine to limit the secondary current and the secondary voltage thereof to a predetermined maximum value, and means for providing a component of magnetic excitation along the secondary commutating axis of said metadyne dynamoelectric machine dependent upon variations in an electrical characteristic of said main dynamoelectric machine to oppose said variations of said electrical characteristic. 

